iOS 7のDynamic Type機能をサポートしてみる ref: http://qiita.com/koogawa@github/items/1011962b444420b854d7

file0.m

+ (UIFont *)systemFontOfSize:(CGFloat)fontSize;

file1.m

+ (UIFont *)preferredFontForTextStyle:(NSString *)style

file2.m

[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(preferredContentSizeChanged:)
name:UIContentSizeCategoryDidChangeNotification
object:nil];